AlphaMask derives from Bitmap so their destructor should be virtual

vcl/inc/vcl/alpha.hxx

@@ -50,7 +50,7 @@ public:
                             AlphaMask( const Bitmap& rBitmap );
                             AlphaMask( const AlphaMask& rAlphaMask );
                             AlphaMask( const Size& rSizePixel, sal_uInt8* pEraseTransparency = NULL );
-                            ~AlphaMask();
+    virtual                 ~AlphaMask();
 
     AlphaMask&              operator=( const Bitmap& rBitmap );
     AlphaMask&              operator=( const AlphaMask& rAlphaMask ) { return (AlphaMask&) Bitmap::operator=( rAlphaMask ); }

vcl/inc/vcl/bitmap.hxx

@@ -420,7 +420,7 @@ public:
                             Bitmap( const Size& rSizePixel, sal_uInt16 nBitCount, const BitmapPalette* pPal = NULL );
                             Bitmap( const ResId& rResId );
                             Bitmap( SalBitmap* pSalBitmap );
-                            ~Bitmap();
+    virtual                 ~Bitmap();
 
     Bitmap&                 operator=( const Bitmap& rBitmap );
     inline sal_Bool             operator!() const;